“Mercy killing” is simply another word for “euthanasia” in most English-language dictionaries. Euthanasia and, therefore, mercy killing is “the act of putting a person or animal to death painlessly or allowing them to die by withholding medical services, usually because of a painful and incurable disease.”
The Greek word euthanasia translates to “good death,” making it and mercy killing terms that can be comforting in the face of difficult medical situations. When any person, especially a family member or close friend, is experiencing pain, mental degeneration, or other adverse condition, our instinct is to relieve the person in any way possible. Sometimes, this desire to alleviate pain can become so strong in the caregiver or patient that it overrides our deeper impulse to preserve life and survive.
This struggle is not new to humanity. In fact, one of the oldest stories in the Bible tells of Job’s desire for death in the midst of his suffering. Job laments his life, even requesting God to kill him rather than allow his pain—emotional, physical and spiritual—to continue (Job 6:8–11). Most pertinently, Job declares, “I prefer strangling and death, rather than this body of mine. I despise my life; I would not live forever. Let me alone; my days have no meaning” (Job 7:15–16).
Does the Bible endorse Job’s feelings? It certainly recognizes that such feelings exist. Other characters in Scripture have, in desperation, asked for an early end to their lives, including Elijah (1 Kings 19:4) and Saul (1 Chronicles 10:4). Scripture acknowledges that emotion and even logic can support the idea of a “mercy killing.” However, we do not live by emotion or logic but by faith (Romans 1:17). God has plans and an understanding we can never grasp. He is the Giver and Sustainer of life (Nehemiah 9:6), and we do not have the right to usurp His authority. Near the end of Job’s story, his friend Elihu warns him, “Beware of turning to evil, which you seem to prefer to affliction” (Job 36:21). It is not our place to decide the time or manner of our death. Mercy killing is a sin against God’s plan and power.
Dietrich Bonhoeffer was a German theologian who had great personal experience with suffering. He was imprisoned and eventually executed by the Third Reich during World War II. While in prison, he wrote this in his Ethics, published posthumously: “The right to the end of life is reserved for God, because only God knows the goal toward which a life is being directed. God alone wishes to be the one who justifies or rejects a life.”
 Got Questions Ministries. (2010). Got Questions? Bible Questions Answered. Bellingham, WA: Logos Bible Software.